Analysing GORK clustering for enhanced stomatal control

气孔是通过植物叶片不透水的角质层提供气体交换的气孔。它们打开和关闭，以平衡光合作用对二氧化碳进入的要求，以及减少水蒸气的蒸腾和防止叶子干燥的需要。气孔蒸腾是水资源供应和作物生产危机的核心，预计这场危机将在未来20-30年内展开：在过去100年里，全球农业用水量增加了6倍，是人类用水量的两倍，预计在2030年前将再翻一番。农业中使用的大部分水都通过气孔孔。因此，气孔是控制作物表现的一个重要目标。值得注意的是，面对环境波动，尤其是光的变化，气孔反应往往延迟。提高水分利用效率(=光合作用中固定的碳量/水分释放量)应该是可能的，而不需要花费光合作用中的碳同化，如果能提高气孔响应的速度。气孔运动是由气孔周围保卫细胞的细胞膜上的溶质运输以及由此引起的水分吸收/损失驱动的。保卫细胞含有离子通道蛋白，以促进气孔运动的阳离子通量。独一无二的是，一类植物离子通道的开放(或门控)也对外界K+浓度敏感。这些通道在烟草、蚕豆和拟南芥的保卫细胞中发现，后者仅由Gork基因编码。外加K+可使通道开放与K+的平衡电压平行，并影响全细胞电导。这些通道是气孔关闭期间K+外流的主要途径，但它们对K+的敏感性限制了K+的转运能力，尤其是在较高的外部K+时。基于最近模型的估计表明，只要这些通道的通量能力适度增加，气孔关闭的速度可以加快3倍。Gork通道对K+的敏感性是通道蛋白本身的特性，这应该有助于操纵K+流出能力来加速气孔关闭。我的实验室已经发现证据表明，Gork门控的K+依赖与它在星团中的组装有关。这些组件需要戈尔克的所谓“电压传感域”(VSD)来相互作用。众所周知，VSD的移动会将电压耦合到沟道选通，因此VSD之间的相互作用很可能提供了一种合作自我调节的机制。我现在建议完成Gork VSD相互作用的分析，以及对通道控制和气孔运动的影响。不管机制如何，很明显，这些发现为探索植物中这类K+通道的独特和基本性质以及操纵通道活动提供了手段，潜在地增强了植物气孔关闭和水分利用的动力学。

Stomata are pores that provide for gaseous exchange across the impermeable cuticle of plant leaves. They open and close to balance the requirement for CO2 entry for photosynthesis against the need to reduce the transpiration of water vapour and prevent leaf drying. Stomatal transpiration is at the centre of a crisis in water availability and crop production that is expected to unfold over the next 20-30 years: globally, agricultural water usage has increased 6-fold in the past 100 years, twice as fast as the human population, and is projected to double again before 2030. The bulk of water used in agriculture passes through the stomatal pore. Thus stomata represent an important target for manipulating crop performance. Significantly, stomatal responses are often delayed in the face of environmental fluctuations, especially of light. Improving water use efficiency (=amount of carbon fixed in photosynthesis/amount of water transpired) should be possible, without a cost to carbon assimilated in photosynthesis, if the speed of stomatal response can be enhanced.Stomatal movements are driven by solute transport - and consequent uptake/loss of water - across the cell membrane of the guard cells which surround the stomatal pore. Guard cells harbour ion channel proteins to facilitate cation flux for stomatal movement. Uniquely, the opening (or gating) of one class of plant ion channels is also sensitive to external K+ concentration. These channels are found in guard cells of tobacco, Vicia and Arabidopsis, in the latter encoded solely by the GORK gene. Increasing K+ outside moderates channel opening in parallel with the equilibrium voltage for K+ and affects whole-cell conductance. These channels are the main pathway for K+ efflux during stomatal closure, but their K+-sensitivity constrains K+ flux capacity, notably at higher external K+. Estimates based on recent modelling suggests that stomatal closure could be accelerated 3-fold with only a moderate increase in the flux capacity of these channels.The K+-sensitivity of the GORK channel is a property of the channel protein itself, which should facilitate manipulating K+ efflux capacity to accelerate stomatal closure. My laboratory has uncovered evidence that the K+-dependence of GORK gating is associated with its assembly in clusters. These assemblies require the the so-called 'voltage-sensor domains' (VSDs) of GORK to interact with one another. Movement of the VSDs is known to couple voltage to channel gating, so it is likely that interaction between VSDs provides a mechanism for cooperative self-regulation. I propose now to complete the analysis of GORK VSD interaction and the consequences for channel control and for stomatal movements. Regardless of the mechanism, it is clear that these discoveries offer the means to explore a unique and fundamental property of this class of K+ channels in plants and to manipulate channel activity, potentially enhancing the kinetics of stomatal closure and water use by the plant.